The present invention relates to a method for making cyclic polyformal by effecting reaction between a bisphenol and a methylene halide in the presence of an alkali metal hydroxide. More particularly, the present invention relates to the use of a phase transfer catalyst to effect contact between a bisphenol dianion in an aqueous phase of a plural phase reaction mixture with a methylene halide, resulting in the production of cyclic polyformal while substantially excluding the formation of linear polyformal.
Prior to the present invention, aromatic polyformal, consisting essentially of chemically combined units of the formula, EQU --OROCH.sub.2 --,
where R is a divalent aromatic radical, was made by effecting reaction between a diphenylate preform and a methylene halide, as shown by Barclay U.S. Pat. No. 3,069,388. An in situ method for making aromatic polyformal is shown in copending application of Allan S. Hay, Ser. No. 739,562, filed Nov. 8, 1976 and Ser. No. 889,393, filed Mar. 23, 1978, which is a continuation-in-part of Ser. No. 739,562, where both applications are assigned to the same assignee as the present invention. As taught by Hay, Ser. No. 889,393, the aromatic polyformal can contain at least 50% by weight of aromatic cyclic polyformal.
In copending application Ser. No. 905,637, of Allen S. Hay, for Cyclic Polyformals and Method For Making, filed concurrently herewith, aromatic cyclic polyformal, based on the use of 1,1-dichloro-2,2-(4-hydroxyphenyl)ethylene, is described which can be used in making wire coating formulations and flame retardants when blended with various organic polymers. Improved yields of aromatic cyclic polyformal is described in the copending application Ser. No. 905,636 of Williams et al, Method for Making Aromatic Cyclic Polyformals, filed concurrently herewith. In Ser. No. 905,636, reaction is effected between a bisphenol dianion and a methylene halide and the resulting aromatic polyformal is extracted with a dialkyl ketone to recover aromatic polyformal cyclics. It would be desirable to provide a method for making aromatic cyclic polyformal of the formula, ##STR1## where R.sup.1 is defined more particularly below and n is an integer equal to 2-25 inclusive, which substantially excludes the formation of linear aromatic polyformal which must be separated therefrom.